The present invention relates to a glass gob cutting device in a gob feeder, and more particularly to a glass gob cutting device which can cut a gob of molten glass and steadily feed the cut gob of molten glass to a glass forming machine.
Most glass articles are manufactured by a process in which raw materials are converted by a furnace to molten glass that is then fed to a glass forming machine and formed into the glass articles.
In general, a gob feeder used for feeding a gob of molten glass to a glass forming machine is known, for example, as disclosed in Japanese Laid Open Publication No. 62-30628. When the above gob feeder is used to mold glass articles, molten glass which has been molten in the furnace is continuously fed to the glass forming machine at regular time intervals. The molten glass fed by the gob feeder is cut by shearing blades which are fixed to tip ends of supporting arms.
Further, the conventional gob feeder is provided with a drop guide for guiding a gob of molten glass which has been cut. The drop guide is fixed to a tip end of a guide arm. The guide arm is connected to an intermediate portion of the supporting arm through a pin joint so that the guide arm is interlocked with the supporting arm. Thus, when the shearing arms are moved to actuate the shearing blades, the guide arm is also moved. Further, the shearing blade and the drop guide make a pair, that is, in a gob feeder having three or four gob supplying lines, there are three or four shearing blades and guides both which are positioned above the shearing arm and the guide arm, respectively. The number of searing blades and guides corresponds to the number of the gob supplying lines.
Currently, there is a tendency in the industry to increase the forming speed of the glass articles, particularly a gob feeder which has gob cutting ability of more than 150 cuts per minute has been manufactured. In this case, the tip end of the supporting arm to which the shearing blade is fixed, is actuated in a short time period of less than 0.4 seconds. The actuating speed of the supporting arm reaches its maximum speed of 2 m/s from its stationary state within 0.4 seconds. This actuation of the supporting arm is repeated twice per cutting cycle, which is frequently repeated.
In the conventional gob feeder, when the supporting arm is actuated at high speed, the guide arm connected to the supporting arm through the pin joint is actuated at high speed. Further, the shearing blade and the guide are fixed to the tip ends of the shearing arm and the guide arm respectively, therefore, both tip ends are heavy. In case of the gob feeder having three or four shearing blades and guides, the tip ends of the shearing arm and the guide arm are heavier due to the number of shearing blades and guides. If the heavy shearing arm and the heavy guide arm are actuated at high speed, the moment of inertia thereof is highly increased. As a result, the shearing arm and the guide arm are not actuated smoothly.
The supporting arm is actuated by a shearing mechanism, incorporating a plurality of gears, provided at a base portion of the supporting arm. If the supporting arm is actuated at high speed and the moment of inertia is highly increased, gears constituting the shearing mechanism wear away in a short time and backlash is formed between gear teeth. Therefore, the gob cannot be normally cut due to the backlash, thereby exerting a bad influence on strength and quality of the glass articles. That is, a shearing mark which is a big cut mark is formed, resulting in inefficient manufacturing process.
Further, if the supporting arm is actuated at high speed, the moment of inertia will be highly increased, and the guide arm for supporting the guide may be damaged or subject to elastic deformation before gears of the shearing mechanism wear away. If the guide arm is damaged, it must be replaced with a new one. If the guide arm is subject to elastic deformation, the guide may be displaced from the regular position for guide. Consequently, when cutting the glass gob, the glass gob cannot be steadily supplied to the glass forming machine.